The mortality patterns of Norway pout (NP) are not well understood. It has been suggested that NP undergo heavy spawning mortality,
and this paper summarizes and provides new evidence in support of this hypothesis. The very low–absent fishing activity in
recent years provides a unique opportunity to analyse the natural life-history traits of cohorts in the NP stock in the North Sea.
Based on the ICES trawl survey abundance indices, cohort mortality is found to significantly increase with age. We argue that this
cannot be explained by selectiveness in the fishery, potential size-specific migrations out of the area, higher predation pressure on
older individuals, or differences in survey catchability by NP age from before to after spawning and that it is higher in the main spawning
areas than outside. We found that natural mortality (M) is significantly correlated with sexual maturity, sex, growth, and intraspecific
stock density. All of this is consistent with a greater mortality occurring mainly from the first to the second quarter of
the year, i.e. spawning mortality, which is discussed as being a major direct and indirect cause of stock mortality